Validation studies of methods purported to disinfect surfaces contaminated with TSE agents approved by CBER Institutional Animal Care and Use Committee and initiated in FY 97 were continued in FY 98. A method originally developed to evaluate the ability of virucides to disinfect surfaces was adapted to test the 263K strain of hamster-adapted scrapie agent as a model for other TSE agents. The method uses disposable equipment in order to reduce the opportunity for artifactual results from cross contamination. Substantial amounts of scrapie infectivity have been demonstrated to remain adherent to glass surfaces after repeated soaking of objects in water and to be recoverable and demonstrable when the glass is pulverized. As suspected, some infectivity has already been found to survive autoclaving for 90 minutes at _134oC. Infectivity has not yet been demonstrated to survive treatments with NaOH, NaOCl, phenolic disinfectants or formic-acid treatments, although the animals used to assay results of those experiments have been on test for only a few months. This project will be continued in FY 99.